Tibial spacer blocks and femoral cutting guide

The present invention relates generally to one or more components used during knee arthroplasty, where the component(s) are used for: performing a range of motion analysis and verifying the flexion and extension gaps between the femur and tibia; verifying the alignment of the femur relative to the mechanical axis; and/or guiding a cutter during resection of the distal femur and/or the posterior femur. More particularly, the present invention relates to one or more tibial spacer blocks, each configured to be temporarily positioned upon a resected proximal portion of a tibia (essentially mimicking the tibial component of the knee prosthesis), for performing a range of motion analysis and for checking flexion and extension gaps prior to cutting the distal femur and/or the posterior femur. Preferably, the spacer blocks each include an attachment arrangement configured and arranged to mate with a complementary attachment arrangement of an alignment tower and/or a femoral cutting guide. The concept of the present invention can be applied to many different types of arthroplasty, such as, for example, Unicompartmental Knee Arthroplasty (UKA) and Total Knee Arthroplasty (TKA).

Throughout this application various positional terms—such as distal, proximal, medial, lateral, anterior and posterior—will be used in the customary manner when referring to the human anatomy. More specifically, “distal” refers to the area away from the point of attachment to the body, while “proximal” refers to the area near the point of attachment the body. For example, the proximal femur refers to the portion of the femur near the hip, while the distal femur refers to the portion of the femur near the tibia. The terms “medial” and “lateral” are also essentially opposites, where “medial” refers to something situated closer to the middle of the body, while “lateral” refers to something situated closer to the left side or the right side of the body (than to the middle of the body). Finally, with regard to anterior and posterior, “anterior” refers to something situated closer to the front of the body and “posterior” refers to something situated closer to the rear of the body.

Also, the term “mechanical axis” of the femur refers to an imaginary line drawn from the center of the femoral head to the center of the distal femur at the knee and the term “anatomic axis” of the femur refers to an imaginary line drawn the middle of the femoral shaft (see <figref idrefs="DRAWINGS">FIG. 6</figref> for examples of the mechanical axis <b>54</b> and the anatomic axis <b>56</b>). The angle between the mechanical axis and the anatomic axis is generally approximately 6°.

The present invention provides an alternative approach to known methods and devices used for guiding the cutting blade for cutting the distal femur or the posterior femur during knee arthroplasty, as well as providing components for checking flexion and extension gaps and defining the amount of limb correction, all prior to cutting the distal femur. For example, one known method of guiding the cutter for cutting the distal femoral condyle (or condyles) uses an intramedullary femoral resection guide (that includes a rod seated within a hole drilled into the distal femur) upon which a distal femoral resector block is fixed, via a post and a pin (which pin is used to select the desired angle of limb correction). However, when using such an intramedullary femoral resection guide, a hole must be drilled into the distal femur to receive the rod of the guide. Additionally, the selected varus/valgus of the particular condyle can only be chosen from a set of predetermined angles provided on the intramedullary femoral resection guide (such as the angles 2°, 4°, 6°, and 8°), with no provisions for other angles, or half angles. Further, such intramedullary femoral resection guides do not provide an associated, attachable device that allows, prior to cutting the distal femur, for a range of motion analysis and for verification of the flexion and extension gaps. Similar problems are also encountered with present methods for cutting the posterior femur as well.

SUMMARY OF THE INVENTION

In one embodiment, the present invention includes a spacer block, or a plurality of blocks of different thicknesses, that are configured to be temporarily positioned upon a resected proximal portion of a tibia, where the spacer block essentially mimics the shape, in the thickness direction (i.e., the distal/proximal direction), of the tibial component of the knee joint prosthesis intended to be implanted. The spacer block can then be used when performing a range of motion analysis, and to check the flexion and extension gaps (of any flexion angle) prior to femoral cutting. This embodiment of the spacer block is also configured to cooperate with an alignment tower, for defining the amount of limb correction, and/or to cooperate with a femoral cutting guide, for aligning a cutting blade used to cut the distal femoral condyle (or condyles) to receive the femoral component of the knee joint prosthesis. The present invention can also be used for cutting the posterior femur by making the cut with the leg in flexion.

More specifically, the present invention provides a spacer block intended to be temporarily positioned upon a resected proximal portion of a tibia during knee arthroplasty. The spacer block preferably includes a main body portion and an attachment arrangement. The main body portion has a thickness defined between substantially parallel distal and proximal surfaces, where the thickness is approximately equal to a corresponding thickness of a tibial component of a knee joint prosthesis. The attachment arrangement is preferably provided on an anterior side of the main body portion, and is configured and arranged to mate with a complementary attachment arrangement of at least one of a femoral cutting guide and an alignment tower.

Additionally, another aspect of the present invention relates to a femoral cutting guide intended to be used during knee arthroplasty, after resection of a tibia, for guiding a cutting member into proper orientation for resecting a distal portion of a femur. The cutting guide preferably includes a slot configured and arranged to receive the cutting member intended to resect a portion of the femur; and an attachment arrangement configured and arranged to mate with a complementary attachment arrangement on a spacer block.

Yet another aspect of the present invention relates to a system of components used during knee arthroplasty, after resection of a tibia, for guiding a cutting member into proper orientation for resecting a portion of a femur. The system preferably includes a femoral cutting guide and a plurality of spacer blocks of different thicknesses. One embodiment of the femoral cutting guide includes a slot configured and arranged to receive the cutting member intended to resect a portion of the femur. In this embodiment of the spacer blocks are each configured to be temporarily positioned upon a resected proximal portion of a tibia during knee arthroplasty, with each of the spacer blocks including a main body portion and an attachment arrangement. The thickness of each main body portion is defined between substantially parallel distal and proximal surfaces, where the thickness of the main body portion of a particular spacer block is approximately equal to a corresponding thickness of a tibial component of a knee joint prosthesis. The attachment arrangement is preferably provided on an anterior side of the main body portion, and the arrangement is preferably configured and arranged to mate with a complementary attachment arrangement on the femoral cutting guide.

The system may also include an alignment tower and an alignment rod. The alignment tower preferably includes a second complementary attachment arrangement, of a similar configuration to the complementary attachment arrangement of the femoral cutting guide. The second complementary attachment arrangement is also configured and arranged to mate with the attachment arrangement of each of the spacer blocks. The alignment rod is preferably configured to be inserted into a hole within the alignment tower, wherein the alignment rod is used for checking the alignment of the limb.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Preferred embodiments of the present invention are described herein with reference to the drawings wherein:

<figref idrefs="DRAWINGS">FIG. 1</figref> is a proximal perspective view, shown from the anterior side, of a first embodiment of the present spacer block;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a distal perspective view, shown from the posterior side, of the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a proximal view of the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a side view of the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 5</figref> is a view of the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref> shown in position between a femur and a tibia;

<figref idrefs="DRAWINGS">FIG. 6</figref> is a view of the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref>, shown in position between a femur and a tibia and with an alignment tower attached, and also showing the anatomic axis and the mechanical axis of the femur, and the mechanical axis of the limb;

<figref idrefs="DRAWINGS">FIG. 7</figref> is an enlarged view of the spacer block and alignment tower of <figref idrefs="DRAWINGS">FIG. 6</figref>, shown rotated approximately 45°;

<figref idrefs="DRAWINGS">FIG. 8</figref> is a proximal perspective view of an embodiment of a femoral cutting guide of the present invention;

<figref idrefs="DRAWINGS">FIG. 9</figref> is a cross-sectional side view of the femoral cutting guide of <figref idrefs="DRAWINGS">FIG. 8</figref>;

<figref idrefs="DRAWINGS">FIG. 10</figref> is a view showing the femoral cutting guide of <figref idrefs="DRAWINGS">FIG. 8</figref> attached to the spacer block of <figref idrefs="DRAWINGS">FIG. 1</figref> and in position between a tibia and a femur;

<figref idrefs="DRAWINGS">FIG. 11</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 10</figref>, except showing the limb in flexion in order to enable the posterior femur to be cut;

<figref idrefs="DRAWINGS">FIG. 12</figref> is a perspective view of a spacer block and femoral cutting guide of a second embodiment of the present invention;

<figref idrefs="DRAWINGS">FIGS. 13A and 13B</figref> are views of a spacer block and a cutting guide of a third embodiment of the present invention, where <figref idrefs="DRAWINGS">FIG. 13A</figref> is a perspective view and <figref idrefs="DRAWINGS">FIG. 13B</figref> is a side view showing (in hidden lines) how the attachment arrangements mate with each other;

<figref idrefs="DRAWINGS">FIGS. 14A and 14B</figref> are views of a spacer block and a cutting guide of a fourth embodiment of the present invention, where <figref idrefs="DRAWINGS">FIG. 14A</figref> is a perspective view and <figref idrefs="DRAWINGS">FIG. 14B</figref> is a side view showing (in hidden lines) how the attachment arrangements mate with each other;

<figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref> are views of a spacer block and a cutting guide of a fifth embodiment of the present invention, where <figref idrefs="DRAWINGS">FIG. 15A</figref> is a perspective view and <figref idrefs="DRAWINGS">FIG. 15B</figref> is a side view showing (in hidden lines) how the attachment arrangements mate with each other; and

<figref idrefs="DRAWINGS">FIG. 16</figref> is a perspective view of a spacer block and a cutting guide of a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to <figref idrefs="DRAWINGS">FIGS. 1-5</figref>, one embodiment of the present spacer block <b>10</b> will be shown and described, with <figref idrefs="DRAWINGS">FIG. 5</figref> showing spacer block <b>10</b> in position between a tibia <b>20</b> and a femur <b>30</b>. As mentioned above, and as shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, spacer block <b>10</b> is configured to be temporarily positioned upon a resected proximal surface <b>12</b> of a tibia <b>20</b> during knee arthroplasty. Once in position, a range of motion analysis can be performed, as well as verification of the flexion and extension gaps, all prior to cutting either the distal portion of the femur or the posterior portion of the femur. Further, this embodiment of the spacer block <b>10</b> also provides an arrangement for attaching either, or both, an alignment tower (such as tower <b>40</b> of <figref idrefs="DRAWINGS">FIG. 7</figref>) and/or a femoral cutting guide (such as cutting guide <b>50</b> of <figref idrefs="DRAWINGS">FIG. 10</figref>).

Spacer block <b>10</b> preferably includes two main components: a main body portion <b>14</b> and an attachment arrangement <b>16</b>. The main body portion is defined between a distal surface <b>22</b> and a proximal surface <b>24</b>. As best shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, the distal surface <b>22</b> is preferably substantially parallel to the proximal surface <b>24</b>. Accordingly, in the thickness direction (i.e., the distal/proximal direction) the body portion <b>14</b> mimics the shape of a tibial component of a knee joint prosthesis. Further, a plurality of spacer blocks <b>10</b> are preferably provided with different thicknesses “t” (<figref idrefs="DRAWINGS">FIG. 4</figref>), whereby the different thicknesses correspond to the different thicknesses of the different tibial components. For example, where the tibial component of a knee joint prosthesis is provided in thicknesses of 8 mm, 10 mm, 12 mm and 14 mm, the spacer block <b>10</b> should be provided with thicknesses “t” of 8 mm, 10 mm, 12 mm and 14 mm. If desired, modular attachments (not shown) of different thicknesses can also be provided to increase the thickness of a block. For example, a 2 mm thick modular attachment can be added to a 10 mm thick spacer block to result in a 12 mm thick spacer block assembly. Of course, the sample thickness dimensions provided here (as well as any other dimensions discussed in this application) are provided by way of example only, and other dimensions are also contemplated as being within the scope of the invention.

The spacer block of the present invention preferably includes markings designating the thickness of the main body portion, such as the 8 mm marking shown in <figref idrefs="DRAWINGS">FIG. 1</figref>. Additional markings are also preferably provided to designate the tibial side and femoral side of the spacer block, such as shown in <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>.

One example of an attachment arrangement <b>16</b> of the spacer block <b>10</b> is shown in <figref idrefs="DRAWINGS">FIGS. 1-5</figref>. In the embodiment shown in the figures, the attachment arrangement includes a projection <b>26</b> of a generally D-shaped cross-section (which D-shaped cross-section can be seen by referring to end portion <b>28</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref>). By utilizing such a cross-section for projection <b>26</b>, inverted attachment of other components (such as alignment tower <b>40</b> or femoral cutting guide <b>50</b>) to the projection <b>26</b> is prevented because the corresponding apertures on the tower or the cutting guide are also generally D-shaped in cross-section (such as aperture <b>42</b> of the tower <b>40</b> of <figref idrefs="DRAWINGS">FIG. 7</figref> and aperture <b>52</b> of the cutting guide <b>50</b> of <figref idrefs="DRAWINGS">FIG. 8</figref>).

Instead of utilizing a generally D-shaped cross-sectional projection (and apertures of corresponding cross-section), other shaped cross-sections are also contemplated as being within the scope of the invention. Preferably, if the D-shaped cross-section is not used, another non-circular cross-section is used in order to still prevent inverted attachment of the tower or the cutting guide to the spacer block. Of course, if the inversion prevention feature is not desired, a projection and a corresponding aperture of circular cross-sections may be used. Further, instead of using attachment arrangements including only a single projection and a single aperture, it is also contemplated that multiple projections and multiple corresponding apertures could also be used (such as in the embodiment of <figref idrefs="DRAWINGS">FIG. 12</figref>). In such instances, the projections and apertures could be of non-circular cross-sections if desired, or they could also be of circular cross-sections, as long as the positions and/or sizes of the projections/apertures prevents inverted attachment, if such a feature is desired. Further, it is also contemplated that the position of the projection(s) and aperture(s) could be reversed, with the projection(s) provided on the alignment tower and the cutting guide, and the aperture(s) provided on the spacer block (such as in the embodiments of <figref idrefs="DRAWINGS">FIGS. 12-16</figref>).

Referring back to the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-5</figref>, projection <b>26</b> also functions as a handle for moving the spacer block into and out of position, in addition to performing the attachment function. In this embodiment, the projection <b>26</b> preferably includes two concave gripping areas <b>32</b>, which facilitate gripping of the spacer block <b>10</b> between two fingers.

In order to help maintain the spacer block <b>10</b> in position upon the resected proximal surface <b>12</b> of the tibia <b>20</b>, as shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, an anterior stop <b>34</b> is preferably provided. As shown in <figref idrefs="DRAWINGS">FIGS. 1-5</figref>, anterior stop <b>34</b> projects from the distal surface <b>22</b> of the spacer block, near the anterior side <b>36</b> of the main body portion <b>14</b>.

In order to further help in maintaining the spacer block <b>10</b> in position, the main body portion <b>14</b> preferably includes at least one aperture configured to receive a pin (either threaded or unthreaded) for pinning the spacer block in position. In this embodiment, a pair of apertures <b>38</b> are preferably provided. Preferably, the apertures <b>38</b> each extend from one of the side walls <b>44</b> or <b>46</b> to the distal surface <b>22</b> of the main body portion <b>14</b>. By placing the apertures <b>38</b> in these locations, the pins can be inserted or removed without being hindered by the distal femur, and the pins do not block usage of the spacer block or any other components attached to the spacer block.

In the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-5</figref>, both the anterior stop <b>34</b> and at least one aperture/pin combination are used together in order to maintain the spacer block in the desired position. However, it is contemplated that either the anterior stop or at least one aperture/pin combination may be used alone. Further, it is also contemplated that different structures or systems for temporarily positioning the spacer block in position may be used either along with the anterior stop and/or the aperture pin combination, or in place of one or more of these structures or systems.

Referring to <figref idrefs="DRAWINGS">FIG. 4</figref>, it can be seen that in this embodiment, the proximal surface <b>24</b> of the main body portion <b>14</b> is not parallel with the proximal surface <b>48</b> of projection <b>26</b>. Instead, an angle θ is defined between proximal surface <b>24</b> and a line extending from surface <b>48</b> (it should be noted that the same angle θ would also be provided between surface <b>48</b> and a line extending from surface <b>24</b>). In this embodiment, angle θ is preferably approximately 5°. An angle θ of approximately 5° accounts for the 5° posterior tibial slope of resected proximal surface <b>12</b> (<figref idrefs="DRAWINGS">FIG. 5</figref>) desired in most patients, while maintaining the projection <b>26</b> normal to the mechanical axis <b>54</b> (see <figref idrefs="DRAWINGS">FIG. 6</figref> for an example of mechanical axis <b>54</b>). The 5° posterior tibial slope is midway between the typical range for most patients of between 3° and 7°, and it is also midway between the extremes of the 0° to 10° found in some patients. Of course, if desired, the angle θ may be set to a value other than 5°.

Turning now to <figref idrefs="DRAWINGS">FIG. 5</figref>, the positioning and use of the spacer block <b>10</b> will be described. Prior to placing the spacer block of the present invention in position, the proximal surface of the tibia <b>20</b> must be resected, using any desired method. After resection, the resulting resected proximal surface <b>12</b> created will be relatively smooth and properly aligned to receive the tibial component of the selected type of knee joint prosthesis (once additional preparation steps of the tibia are completed, such as drilling spaces to receive the pegs of the implant). However, prior to implanting the tibial component, spacer block <b>10</b> is temporarily seated upon the resected proximal surface <b>12</b> of the tibia. The spacer block <b>10</b> used will be of the same thickness as the tibial component intended to be implanted, in order for the spacer block to mimic the tibial component during analysis. Thus, a spacer block <b>10</b> of the appropriate thickness is chosen to be the same as the thickness of the tibial component selected. The spacer block <b>10</b> of the selected thickness is seated upon resected surface <b>12</b>, and moved in the posterior direction, until anterior stop <b>34</b> contacts the anterior surface of the proximal portion of the tibia <b>20</b>.

In the example shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, the medial condyle of the left leg is damaged, and will be removed in a Unicompartmental Knee Arthroplasty (UKA) procedure. Accordingly, the spacer block <b>10</b> is positioned distal of the femoral medial condyle. Of course, if the lateral femoral condyle were being removed, the spacer block would be placed distal of the lateral femoral condyle. Regardless of whether the lateral or medial condyle is being removed, and regardless of whether it is on the right leg or the left leg, the same spacer block <b>10</b> can be used because each of the spacer blocks of a particular thickness has been designed for universal application.

Further, if both lateral and medial condyles are being removed, such as for a Total Knee Arthroplasty (TKA) procedure, the same spacer block may be used twice (once for one condyle, and then, repositioned for the other condyle or simultaneously with two condyles). In the alternative, a spacer block of a width (in the medial/lateral direction) that is approximately double that of the embodiment shown in <figref idrefs="DRAWINGS">FIGS. 1-5</figref> may also be used, such that a single spacer block (not shown) can be seated distal of both the lateral and medial condyles at the same time.

When the spacer block <b>10</b> is properly positioned between the appropriate condyle and the resected proximal surface <b>12</b> of the tibia <b>20</b>, a pin <b>58</b> is inserted into each of the apertures <b>38</b>. As mentioned above, pins <b>58</b> may be threaded or not threaded, as long as they are of a configuration that can be securely inserted into the proximal tibia, as well as being easily removable when the spacer block needs to be removed. The combination of the pins <b>58</b> and the anterior projection <b>26</b> maintain the spacer block <b>10</b> in position upon the resected proximal surface <b>12</b>.

After the spacer block <b>10</b> is secured in position, the tibia can be moved to perform a range of motion analysis, and the flexion and extension gaps can be checked. If it is determined that a different thickness of tibial component is needed, the spacer block can be replaced with another spacer block of an appropriate thickness that corresponds to the new thickness of the tibial component, and the range of motion analysis can be performed again.

Turning now to <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref>, the attachment and use of alignment tower <b>40</b> will be described. Alignment tower <b>40</b> includes an attachment arrangement that is configured to mate with the attachment arrangement <b>16</b> of the spacer block <b>10</b>. In this embodiment, the complementary attachment arrangement of the alignment tower consists of an aperture <b>42</b> of a generally D-shaped cross-section. Aperture <b>42</b> preferably extends the full length of the attachment arm <b>60</b> of the alignment tower. However, in order to better show the placement of projection <b>26</b> within aperture <b>42</b>, some of the hidden lines representing the aperture <b>42</b> have been omitted.

This embodiment of alignment tower <b>40</b> includes other apertures, apertures <b>62</b> and <b>63</b>, which each extend through rod arm <b>64</b>. Apertures <b>62</b> and <b>63</b> are both configured to receive alignment rod <b>66</b>, and either one may be used, depending upon the size of the patient's leg. As shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, alignment rod <b>66</b> is aligned with the mechanical axis <b>54</b> of the femur <b>30</b> to verify that the spacer block (and subsequently the cuts for the femoral component) are properly aligned. If the alignment rod <b>66</b> does not align with the mechanical axis <b>54</b>, a thicker or a thinner spacer block is substituted for the original spacer block, with such substitutions continuing until the desired alignment is achieved. If necessary, the proximal surface <b>12</b> of the tibia can also be re-cut in order to obtain the proper alignment. Once the alignment has been verified, the alignment tower <b>40</b> is removed from the spacer block <b>10</b>.

Turning now to <figref idrefs="DRAWINGS">FIGS. 8 through 10</figref>, one embodiment of the femoral cutting guide <b>50</b> of the present invention will be described. <figref idrefs="DRAWINGS">FIG. 8</figref> shows an anterior (or front) perspective view of femoral cutting guide <b>50</b>, which is configured to be used for guiding a cutting blade when cutting the distal portion of one of the condyles (or for cutting the posterior portion of a condyle, when the limb is in flexion), and <figref idrefs="DRAWINGS">FIG. 9</figref> shows a cross-section of the femoral cutting guide <b>50</b> of <figref idrefs="DRAWINGS">FIG. 8</figref>. <figref idrefs="DRAWINGS">FIG. 10</figref> shows the femoral cutting guide in position, attached to the spacer block.

Femoral cutting guide <b>50</b> includes an attachment arrangement that is the complement of the attachment arrangement of the spacer block <b>10</b>. In the embodiment of <figref idrefs="DRAWINGS">FIGS. 8-10</figref>, the attachment arrangement of guide <b>50</b> includes an aperture <b>52</b> that is of a generally D-shaped cross-section, which is configured to mate with projection <b>26</b> of the spacer block <b>10</b> (see <figref idrefs="DRAWINGS">FIG. 1</figref>). As mentioned above, other configurations of attachment arrangements are also contemplated as being within the scope of the invention.

Femoral cutting guide <b>50</b> also includes a slot that is configured to receive and guide a cutting member, such as blade <b>71</b> shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. Blade <b>71</b> is attached to a reciprocating or oscillating saw (not shown), or other cutting device configured for use during knee arthroplasty.

Projecting from the posterior side of cutting guide <b>50</b> is a ledge <b>70</b>, which is located distal of the slot <b>68</b> and proximal of aperture <b>52</b>. Ledge <b>70</b> is configured to be seated above the proximal surface <b>24</b> of the main body portion <b>14</b> of the spacer block <b>10</b> (<figref idrefs="DRAWINGS">FIG. 1</figref>), with some clearance therebetween.

In order to maintain cutting guide <b>50</b> in position, an aperture <b>72</b> is preferably provided proximal of slot <b>68</b>. Aperture <b>72</b>, if provided, is used with a pin, such as pin <b>74</b> of <figref idrefs="DRAWINGS">FIG. 10</figref>. Although a threaded version of pin <b>74</b> is shown in <figref idrefs="DRAWINGS">FIG. 10</figref>, a non-threaded pin can also be used. In use, pin <b>74</b> is inserted through aperture <b>72</b>, and into the femur <b>30</b>, to more securely maintain cutting guide <b>50</b> in position.

Referring again to the embodiment of <figref idrefs="DRAWINGS">FIGS. 8 and 9</figref>, it can be seen that the distal posterior surface <b>76</b> and the proximal posterior surface <b>78</b> are not perpendicular to either the proximal surface <b>80</b> or the distal surface <b>82</b> (or to the outer aperture surface <b>81</b>). Nor are distal posterior surface <b>76</b> and proximal posterior surface <b>78</b> perpendicular to proximal ledge surface <b>84</b> or to distal ledge surface <b>86</b>, respectively. Instead, there is an angle ax between proximal posterior surface <b>78</b> and proximal ledge surface <b>84</b>, and there is an angle β between distal ledge surface <b>86</b> and distal posterior surface <b>76</b>. In this embodiment, angle ax is approximately 120° and angle β is approximately 95°. Of course, if desired, other angles may also be utilized. Angle α is provided to allow for cutting guide <b>50</b> to be seated as closely as possible with respect to the anterior condyle, and angle β is provided to allow the cutting guide to be seated as closely as possible with respect to the anterior side <b>36</b> of the main body portion <b>14</b> of the spacer block (<figref idrefs="DRAWINGS">FIG. 4</figref>). If there is a change in the angle that the anterior side of the main body portion of the spacer block makes with the projection <b>26</b>, then angle β could also be changed accordingly.

In use, femoral cutting guide <b>50</b> is attached to the spacer block <b>10</b> as shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. More specifically, the aperture <b>52</b> of the cutting guide <b>50</b> is mated with projection <b>26</b> of the spacer block <b>10</b> until the proximal posterior surface <b>78</b> contacts femur <b>30</b>. The distal posterior surface <b>76</b> of the cutting guide <b>50</b> may make contact with the anterior side <b>36</b> of the main body portion <b>14</b> of the spacer block <b>10</b>, or, preferably, there is a slight gap between these two surfaces. There is also preferably a slight gap between the distal ledge surface <b>86</b> of the cutting guide <b>50</b> and the proximal surface <b>24</b> of the spacer block <b>10</b>. Additionally, at this point, the concave gripping areas <b>32</b> of projection <b>26</b> will be located completely outside of aperture <b>52</b>.

As mentioned above, in this first embodiment, the projection <b>26</b> preferably includes two concave gripping areas <b>32</b>, which facilitate gripping of the spacer block <b>10</b>, as mentioned above. In order to enable adequate gripping of the spacer block <b>10</b> when the cutting guide <b>50</b> is attached thereto, preferably, at least about a third of the length of the projection <b>26</b> projects outwardly from the aperture <b>52</b>, such as shown in <figref idrefs="DRAWINGS">FIG. 10</figref>.

If desired, pin <b>74</b> may be inserted through aperture <b>72</b> and into femur <b>30</b>, to more securely maintain the femoral cutting guide <b>50</b> in the intended position. Next, slot <b>68</b> is used as a guide to guide blade <b>71</b> while cutting the distal condyle. After cutting of the distal condyle is completed, the cutting guide <b>50</b> is removed from the spacer block <b>10</b>, and the spacer block is removed from its location.

As mentioned above, the present invention may also be used to cut the posterior condyle. <figref idrefs="DRAWINGS">FIG. 11</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 10</figref>, except with the leg in flexion to enable the posterior condyle to be cut. The procedure for cutting the posterior condyle is essentially the same as that described above for cutting the distal condyle, except that the leg is in flexion, as shown in <figref idrefs="DRAWINGS">FIG. 11</figref>.

In order to finish the femur, any other cuts that need to be made, such as the posterior chamfer or drilling the holes for the pegs of the tibial component, can be made by any desired method. Likewise, the remainder of the procedure relating to <b>1</b>I implanting a prosthetic knee also continues using any desired method.

Turning now to <figref idrefs="DRAWINGS">FIGS. 12-16</figref>, various alternate embodiments of the present invention are shown. Where appropriate, the same reference numbers as those used for the first embodiment will be used in these alternate embodiments, except for the addition of the prime designation. Unless otherwise noted, the embodiments of <figref idrefs="DRAWINGS">FIGS. 12-16</figref> are used in the same manner as the first embodiment, and only the significant differences between these embodiments and the first embodiment will be described.

The embodiments of <figref idrefs="DRAWINGS">FIGS. 12-16</figref> each include a spacer block <b>10</b>′ of a generally half-circular shape, as opposed to the generally rectangular shape of spacer block <b>10</b> of <figref idrefs="DRAWINGS">FIGS. 1-11</figref>. However, either shape, as well as other similar shapes, may be utilized in any of the embodiments. Further, although the drawing figures for the embodiments of <figref idrefs="DRAWINGS">FIGS. 12-16</figref> only show the spacer blocks <b>10</b>′ and the femoral cutting guides <b>50</b>′, alignment towers should also be provided to cooperate with the spacer blocks <b>10</b>′. Although the alignment towers for the embodiments of <figref idrefs="DRAWINGS">FIGS. 12-16</figref> are not shown, the associated alignment towers will be essentially the same as alignment tower <b>40</b> of <figref idrefs="DRAWINGS">FIG. 7</figref>, except that the structure for attaching the alignment tower to the spacer block may not include apertures <b>42</b>, but will instead include the same attachment arrangement found on the femoral cutting guide associated with each particular embodiment of spacer block.

Referring now to the embodiment of <figref idrefs="DRAWINGS">FIG. 12</figref>, this embodiment includes femoral cutting guide <b>50</b>′ and spacer block <b>10</b>′, which are configured to be attached to each other via an attachment arrangement and a complementary attachment arrangement that are different from the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-11</figref>. More specifically, this embodiment includes one or more apertures <b>27</b> on spacer block <b>10</b>′ and corresponding projection(s) <b>53</b> on the femoral cutting guide <b>50</b>′. It should be noted that although three aperture/projections sets are included in the example of this embodiment shown in <figref idrefs="DRAWINGS">FIG. 12</figref>, one, two, four or more projection/aperture sets can be provided if desired. Further, although the three aperture/projection sets are arranged in a generally triangular format with respect to each other (which prevents inverted assembly), such a configuration is not required, because other configurations, including those that do not prevent inverted assembly, are also contemplated as being within the scope of the invention.

Another difference between this embodiment and the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-11</figref> is that the femoral cutting guide <b>50</b>′ is a bit larger than cutting guide <b>50</b> of the first embodiment, and it also includes more apertures <b>72</b>′ than that single aperture <b>72</b> shown in <figref idrefs="DRAWINGS">FIGS. 8 and 9</figref>. The use of more apertures in this embodiment provides the surgeon with more options for placement of one or more pins (such as pin <b>74</b> of <figref idrefs="DRAWINGS">FIG. 10</figref>), while the single aperture configuration of the first embodiment provides a more compact guide that requires less material to manufacture. Of course, any of the embodiments can be made with either a single aperture or with multiple apertures.

Additionally, the spacer block <b>10</b>′ shown in <figref idrefs="DRAWINGS">FIG. 12</figref> lacks an anterior stop (such as anterior stop <b>34</b> shown in <figref idrefs="DRAWINGS">FIGS. 1-5</figref>). If desired, apertures (not shown) can be added to spacer block <b>10</b>′ to be used with pins maintain the spacer block in position upon the tibia, or the spacer block can simply be held in position. Additionally, any other means of maintaining the spacer block in position can also be used.

The embodiment of <figref idrefs="DRAWINGS">FIGS. 13A and 13B</figref> is very similar to the <figref idrefs="DRAWINGS">FIG. 12</figref> embodiment, except this embodiment utilizes a single generally D-shaped projection <b>53</b> that mates with a single generally D-shaped aperture <b>27</b>. The attachment arrangements of this embodiment differ from the generally D-shaped attachment arrangements of the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-11</figref> by being reversed (i.e., in the FIG. <b>13</b>A/<b>13</b>B embodiment, the projection is on the femoral cutting guide and the aperture is on the spacer block, while in the embodiment of <figref idrefs="DRAWINGS">FIGS. 1-11</figref> the projection is on the spacer block and the aperture is on the femoral cutting guide).

The embodiment of <figref idrefs="DRAWINGS">FIGS. 14A and 14B</figref> is very similar to the embodiment of <figref idrefs="DRAWINGS">FIGS. 13A and 13B</figref>, except with regard to the manner in which the posterior tibial slope is accounted for. In the first embodiment of <figref idrefs="DRAWINGS">FIGS. 1-11</figref>, as well as in the second embodiment of <figref idrefs="DRAWINGS">FIG. 12</figref> and the third embodiment of FIGS. <b>13</b>A/<b>13</b>B, the posterior tibial slope is accounted for by angling the portion of the attachment arrangement found on the spacer block with respect to the generally parallel attachment arrangement and cutting slot on the cutting guide. For example, in the first embodiment, <figref idrefs="DRAWINGS">FIG. 4</figref> shows how the projection <b>26</b> of the attachment arrangement of the spacer block <b>10</b> is offset by angle θ, while <figref idrefs="DRAWINGS">FIG. 9</figref> shows that the cutting slot <b>68</b> and the aperture <b>52</b> of the attachment arrangement of femoral cutting guide <b>50</b> are generally parallel to each other, and are not offset. Similarly, the embodiment of <figref idrefs="DRAWINGS">FIGS. 13A and 13B</figref> includes apertures <b>27</b> that are offset, while projections <b>53</b> are not offset, and are generally parallel with cutting slot <b>68</b>′, as best shown in <figref idrefs="DRAWINGS">FIG. 13B</figref>.

In contrast, in the embodiment of <figref idrefs="DRAWINGS">FIGS. 14A and 14B</figref>, the apertures <b>27</b> are not offset, nor are projections <b>53</b>, as best shown in <figref idrefs="DRAWINGS">FIG. 14B</figref>, but instead the cutting slot <b>68</b>′ is offset by angle θ with respect to projection <b>53</b>. Angle θ is the same angle θ defined with respect to <figref idrefs="DRAWINGS">FIG. 4</figref>, and therefore it is preferably 5°, although other angles may also be used, such as any angle between 0° and 10°, and more preferably any angle between 3° and 7°. The alternate arrangement for accounting for the posterior tibial slope described in this embodiment may be substituted for the arrangement provided for in any of the other embodiments.

The embodiment of <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref> includes another different arrangement for accounting for the posterior tibial slope. In this embodiment, as best seen in <figref idrefs="DRAWINGS">FIG. 15B</figref>, the projection <b>53</b> extending from the femoral cutting guide <b>50</b>′ is offset by angle θ, while the apertures <b>27</b> of the spacer block <b>10</b> and the cutting slot <b>68</b>′ are not offset. Once again, this further alternate arrangement for accounting for the posterior tibial slope may also be substituted for the arrangement provided for in any of the other embodiments. In general, the posterior tibial slope may be accounted for by providing an offset in the attachment arrangement of the spacer block (whether projection(s) or aperture(s)) or by providing the offset in the attachment arrangement of the femoral cutting guide and alignment tower (whether projection(s) or aperture(s)), or it may be accounted for by provided the offset in the cutting slot.

The FIG. <b>15</b>A/<b>15</b>B embodiment also includes another feature not shown on the other embodiments, but which can be included in most of the other embodiments if desired—chamfers <b>11</b>. (Chamfers <b>11</b> are not necessary in the first embodiment (<figref idrefs="DRAWINGS">FIGS. 8 and 9</figref>) because no excess material is provided adjacent the aperture <b>72</b>.) The pair of chamfers <b>11</b> may optionally be provided on the femoral cutting guide <b>50</b>′ in order to reduce the material required to manufacture guide <b>50</b>′, and also to avoid potential obstructions caused by portions of a particular femur, which may otherwise hinder a close relationship between the cutting guide and the femur.

An additional embodiment is shown in <figref idrefs="DRAWINGS">FIG. 16</figref>. The femoral cutting guide <b>50</b>′ of this embodiment is essentially the same as the femoral cutting guide <b>50</b> shown in <figref idrefs="DRAWINGS">FIGS. 8 and 9</figref> of the first embodiment, except that the attachment arrangement is a generally D-shaped projection (as opposed to the generally D-shaped aperture <b>52</b> of <figref idrefs="DRAWINGS">FIGS. 8 and 9</figref>). Thus, the male and female portions of the attachment arrangements of this embodiment are reversed when compared with the first embodiment. However, as mentioned above, other attachment arrangements can be substituted for those shown in a specific embodiment.

Other than the type of attachment arrangement, the spacer block <b>10</b>′ of <figref idrefs="DRAWINGS">FIG. 16</figref> is essentially the same as those of the embodiments of <figref idrefs="DRAWINGS">FIGS. 12-15</figref>, except this embodiment also includes a plurality of additional apertures <b>88</b> and a modular hook <b>90</b>. The additional apertures <b>88</b>, which are optional in this embodiment and which can be added to any of the other embodiments, are provided to allow the surgeon to pin the spacer block to the tibia. In use, a pin (such as pin <b>58</b> of <figref idrefs="DRAWINGS">FIG. 5</figref>) is inserted into one or more of the apertures <b>88</b> to maintain the spacer block in position upon the tibia. Modular hook <b>90</b> performs the same function as anterior stop <b>34</b> shown in <figref idrefs="DRAWINGS">FIGS. 1-5</figref>. Accordingly, modular hook <b>90</b> may be used instead of anterior stop <b>34</b> in the first embodiment, and it may be added to any of the other embodiments as well. In the example of modular hook <b>90</b> shown in <figref idrefs="DRAWINGS">FIG. 15</figref>, hook <b>90</b> is secured to the distal surface <b>22</b>′ of the spacer block <b>10</b>′ via a screw, or other easily removably attachment means. Accordingly, the modular hook <b>90</b> can easily be repositioned on the opposite side of the spacer block when the other aperture <b>27</b> is mated with the projection <b>53</b>. Additionally, distal surface <b>22</b>′ preferably includes a recessed portion <b>23</b> to allow the spacer block <b>10</b>′ to sit in a relatively flat manner upon the resected proximal surface of the tibia when the hook <b>90</b> is in position.

While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.